Project Summary Sexual minority women (SMW; lesbian, bisexual, other non-heterosexual women) are at substantially increased risk for substance use (SU) compared to heterosexual women. This is particularly evident in emerging adulthood (ages 18-25), when SMW are at high risk for cannabis and heavy alcohol use. These robust disparities highlight the need to understand and reduce SU among SMW. However, the limitations of existing research hinder efforts to do so. First, research on SU among SMW has almost exclusively used cross-sectional and semi-annual longitudinal designs. While these studies provide a foundation for understanding SU risk among SMW, these methods are limited in the data they can provide about SU risk. Experience sampling methods (ESM) can advance our understanding by identifying temporally proximal risk factors for SU (e.g., factors predicting same/next-day SU) and disentangling risk factors from correlates ? resulting in clearer intervention targets for SMW. Second, SMW are treated as a homogeneous group, so we know little about risk factors for subgroups of SMW (i.e., lesbian, bisexual, queer, pansexual). This is a critical problem because 1) preliminary evidence suggests that one factor (sexual identity disclosure) is linked to SU for bisexual, but not lesbian, women; 2) a subset of SMW?those with multi-gender attractions?experience unique stressors theorized to impact SU, and 3) shared risk factors (e.g. peer influences) may differentially impact subgroups of SMW. Despite their risk, there are no SU interventions tailored for SMW, highlighting the need to determine how to adapt SU interventions to address their unique risk factors. The goals of the proposed study are to: 1) identify risk factors for problematic cannabis and alcohol use among emerging adult SMW; 2) delineate common and unique risk factors for subgroups of SMW; and 3) determine how to adapt a SU intervention for SMW. These goals will be met using a mixed methods approach. Phase 1 will consist of a 30-day ESM study of self-identified lesbian, bisexual, queer, and pansexual emerging adult women (60 per identity) and will focus on identifying within- and between-person risk factors for SU and delineating common and unique risk factors for subgroups of SMW. In Phase 2, we will conduct qualitative interviews with 60 Phase 1 participants. Interviews will focus on perceived risk factors for SU, SMW?s interpretations of ESM findings, and ways to adapt a SU intervention for SMW. This award will provide the applicant with training in SU research, ESM, qualitative/mixed-methods, and intervention development at Northwestern University?s Institute for Sexual and Gender Minority Health and Wellbeing ? a rich intellectual environment with abundant resources ideal for training scholars in sexual minority health research. The training and research activities funded by this K01 will facilitate the applicant?s transition to an independent investigator with a program of translational research focused on understanding and reducing SU disparities affecting SMW.